Using Oceanography To Help North Atlantic Right Whales
Off the coast of South Jersey, lucky whale watchers may sometimes glimpse a critically endangered North Atlantic right whale (Eubalaena glacialis). Despite protections in the United States (US) from whaling since 19351, this baleen whale species has struggled to recover, with only about 340 individuals remaining in the world2 . Although most right whales summer off of Maine and Canada and travel to Georgia and Florida during the winters, not all of them migrate every year, meaning that individual right whales can be found all along the east coast of the US during most of the year3. Beyond the normal challenges of trying to study a marine animal (lack of light and GPS signal underwater for starters!), right whales are moving. They have abandoned some of the habitats they traditionally use during some parts of the year, and are taking up residency in previously unused spots.
One of these new year-round habitats is located south of Nantucket Island off of Massachusetts4. Researchers at the Anderson Cabot Center for Ocean Life at the New England Aquarium, who noticed the shift during aerial surveys, partnered with Rutgers University to try to understand what was going on. And I was the graduate student who tackled this mystery in my thesis.
We used a data product from the University of Delaware, which combines sea surface temperature and ocean color, measured via satellite, to define distinct ocean masses, or bodies, within the ocean5. Sea surface temperature has undergone dramatic changes due to climate change. Ocean color measures how light reflects off the ocean at different wavelengths, and is connected to plankton concentrations- very useful considering that right whales eat tiny zooplankton called copepods. The figures below give an idea of these water masses: on the top, each color represents a different water
mass, and the map on the bottom shows the gradient (or how different one mass is from its neighbor) between the masses.
We compared 2 time frames: the 3 years before the whales moved, and the 3 years after the change. We looked at how many water masses were in the study area each day. We analyzed which water masses were present in each season, and how they changed over time. We looked at how the gradient values shifted from one time frame to the other6. And we found some interesting information.
Based on the change in prevalence of different water masses in the study area, we learned that
the water had cooled in the winter and fall months over time, but had warmed during the spring months. The changing temperatures impact the life cycles of those delicious copepods. We also discovered that a greater percentage of the study area was occupied by stronger fronts (caused by the gradients between water masses) during the second time frame6, supporting previous findings that right whales tend to cluster around strong fronts7,8.
So how does this help the whales? The Anderson Cabot Center is currently working to build habitat models, so we can start to predict where these whales will be, and when. Better predictions mean we can protect the spots where the whales are, with things like vessel speed reductions and fishing regulations. Reducing ship strikes and fishing gear entanglements will go a long way toward protecting this vulnerable species, and understanding the ocean conditions in their habitat will go a long way towards strengthening those habitat models.
So the next time you are on the American Star, keep an eye out for the distinctive V-shaped
blow spout of a North Atlantic right whale. With continued research, technological advances and
protective policies, improving the odds of spotting one of these amazing creatures from 1 in 340 can be a reality.
-Rhyan Grech, Intern at Cape May Whale Watch and Research Center
Rutgers University ’23
1Kraus, S. D., & Rolland, R. (Eds). (2007). The urban whale: North Atlantic right whales at the crossroads. Harvard University Press.
2Pettis, H. M., Pace, R. M. I., & Hamilton, P. K. (2023). North Atlantic Right Whale Consortium 2022 annual report card. North Atlantic Right Whale Consortium. https://www.narwc.org/uploads/1/1/6/6/116623219/2022reportcardfinal.pdf
3Davis, G. E., Baumgartner, M. F., Bonnell, J. M., Bell, J., Berchok, C., Bort Thornton, J., Brault, S., Buchanan, G., Charif, R. A., Cholewiak, D., Clark, C. W., Corkeron, P., Delarue, J., Dudzinski, K., Hatch, L., Hildebrand, J., Hodge, L., Klinck, H., Kraus, S., . . . Van Parijs, S. M. (2017). Long-term passive acoustic recordings track the changing distribution of North Atlantic right whales (Eubalaena glacialis) from 2004 to 2014. Scientific reports, 7(1), 13460. https://doi.org/10.1038/s41598-017-13359-3
4O’Brien, O., Pendleton, D. E., Ganley, L. C., McKenna, K. R., Kenney, R. D., Quintana-Rizzo, E., Mayo, C. A., Kraus, S. D., & Redfern, J. (2022). Repatriation of a historical North Atlantic right whale habitat during an era of rapid climate change. Scientific reports, 12(1), 12407-12407. https://doi.org/10.1038/s41598-022-16200-8
5Oliver, M. J., Glenn, S., Kohut, J. T., Irwin, A. J., Schofield, O. M., Moline, M. A., & Bissett, W. P. (2004). Bioinformatic approaches for objective detection of water masses on continental shelves. Journal of Geophysical Research, 109(C7), C07S04-n/a. https://doi.org/10.1029/2003JC002072
6Grech, R. (2023). Impacts of Oceanic Conditions on North Atlantic Right Whale Distribution on the Nantucket Shoals [Unpublished master’s thesis]. Rutgers University.
7Baumgartner, M. F., Cole, T. V. N., Campbell, R. G., Teegarden, G. J., & Durbin, E. G. (2003). Associations between North Atlantic right whales and their prey, Calanus finmarchicus, over diel and tidal time scales. Marine ecology. Progress series (Halstenbek), 264, 155-166. https://doi.org/10.3354/meps264155
8Dreyfus, C. (2022). Aligning the seasonal migration of North Atlantic Right Whales with oceanic features (Publication No. 29394988) [Master’s Thesis, Rutgers University]. ProQuest Dissertations & Theses Global. https://doi.org/doi:10.7282/t3-fw3e-2z09